Colostrum is a unique food supplement, rich in a variety of biologically active proteins. It is the first “milk” given to a newborn calf by its mother, and contains many bioactive compounds not present in ordinary milk. Colostrum is normally secreted only in the first 48 to 72 hours after birth. Source Naturals Colostrum is true, bovine colostrum (not cheese whey), collected within the first 12 hours of production. It is then standardized, so that the key proteins found in colostrum make up 30% of the finished product.